I think performance is one of the reasons, if not the main reason why WhatsApp is the leading mobile chat application. They can manage more millions of message

I think performance is one of the reasons, if not the main reason why WhatsApp is the leading mobile chat application. They can manage more millions of messages per second than all their competitors. The 'build slower applications much faster' mantra has some value, except when everyone can build that application in a month and the market is full of clones.